Kotlin2 equals + hashcode + toString

graphql-dgs-codegen-core/src/integTest/kotlin/com/netflix/graphql/dgs/codegen/Kotlin2CodeGenTest.kt

@@ -333,6 +333,68 @@ class Kotlin2CodeGenTest {
         assertCompilesKotlin(result)
     }
 
+    @Test
+    fun `equals and hashCode compare requested fields by value, at runtime`() {
+        val schema =
+            """
+            type Item {
+                name: String
+                age: Int
+            }
+            """.trimIndent()
+
+        val result =
+            CodeGen(
+                CodeGenConfig(
+                    schemas = setOf(schema),
+                    packageName = "com.netflix.test.equalshashcode",
+                    language = Language.KOTLIN,
+                    generateKotlinNullableClasses = true,
+                    generateKotlinClosureProjections = true,
+                ),
+            ).generate()
+
+        val buildDir = assertCompilesKotlin(result)
+        val classLoader = URLClassLoader(arrayOf(buildDir.toUri().toURL()), this.javaClass.classLoader)
+        val builderClass = classLoader.loadClass("com.netflix.test.equalshashcode.types.Item\$Builder")
+        val withNameMethod = builderClass.getMethod("withName", String::class.java)
+        val withAgeMethod = builderClass.getMethod("withAge", Integer::class.java)
+        val buildMethod = builderClass.getMethod("build")
+
+        fun newItem(
+            name: String?,
+            requestName: Boolean,
+            age: Int?,
+            requestAge: Boolean,
+        ): Any {
+            val builder = builderClass.getDeclaredConstructor().newInstance()
+            if (requestName) withNameMethod.invoke(builder, name)
+            if (requestAge) withAgeMethod.invoke(builder, age)
+            return buildMethod.invoke(builder)
+        }
+
+        // Same projection, same values -> equal, and hashCode is consistent with equals.
+        val sameProjectionA = newItem("Alice", requestName = true, age = 30, requestAge = true)
+        val sameProjectionB = newItem("Alice", requestName = true, age = 30, requestAge = true)
+        assertThat(sameProjectionA).isEqualTo(sameProjectionB)
+        assertThat(sameProjectionA.hashCode()).isEqualTo(sameProjectionB.hashCode())
+
+        // `age` requested on only one side -> not equal, in both directions, and does not throw.
+        val onlyNameRequested = newItem("Alice", requestName = true, age = null, requestAge = false)
+        assertThat(sameProjectionA).isNotEqualTo(onlyNameRequested)
+        assertThat(onlyNameRequested).isNotEqualTo(sameProjectionA)
+
+        // `age` unrequested on both sides -> equal without invoking the throwing supplier.
+        val onlyNameRequestedTwin = newItem("Alice", requestName = true, age = null, requestAge = false)
+        assertThat(onlyNameRequested).isEqualTo(onlyNameRequestedTwin)
+        assertThat(onlyNameRequested.hashCode()).isEqualTo(onlyNameRequestedTwin.hashCode())
+
+        // `age` requested-but-null vs. `age` absent -> not equal.
+        val nameRequestedNullAge = newItem("Alice", requestName = true, age = null, requestAge = true)
+        assertThat(onlyNameRequested).isNotEqualTo(nameRequestedNullAge)
+        assertThat(nameRequestedNullAge).isNotEqualTo(onlyNameRequested)
+    }
+
     companion object {
         @Suppress("unused")
         @JvmStatic

graphql-dgs-codegen-core/src/integTest/kotlin/com/netflix/graphql/dgs/codegen/cases/constantsForInputTypes/expected/types/Person.kt

@@ -7,7 +7,11 @@ import com.fasterxml.jackson.databind.`annotation`.JsonDeserialize
 import com.fasterxml.jackson.databind.`annotation`.JsonPOJOBuilder
 import com.netflix.graphql.dgs.codegen.cases.constantsForInputTypes.expected.Generated
 import java.lang.IllegalStateException
+import kotlin.Any
+import kotlin.Boolean
+import kotlin.Int
 import kotlin.String
+import kotlin.collections.List
 import kotlin.jvm.JvmName
 
 @Generated
@@ -29,6 +33,24 @@ public class Person(
   public val lastname: String?
     get() = __lastname.invoke()
 
+  private fun `__$fieldValues`(): List<Any?> = listOf(
+      if (__firstname === firstnameDefault) firstnameDefault else firstname,
+      if (__lastname === lastnameDefault) lastnameDefault else lastname,
+  )
+
+  override fun equals(other: Any?): Boolean = this === other || (other is Person &&
+      `__$fieldValues`() == other.`__$fieldValues`())
+
+  override fun hashCode(): Int = `__$fieldValues`().hashCode()
+
+  private fun `__$fieldStrings`(): List<String> = listOfNotNull(
+      if (__firstname === firstnameDefault) null else "firstname=" + firstname,
+      if (__lastname === lastnameDefault) null else "lastname=" + lastname,
+  )
+
+  override fun toString(): String = `__$fieldStrings`().joinToString(prefix = "Person(", postfix =
+      ")")
+
   @Generated
   public companion object {
     private val firstnameDefault: () -> String? = 

graphql-dgs-codegen-core/src/integTest/kotlin/com/netflix/graphql/dgs/codegen/cases/constantsForInputTypes/expected/types/Query.kt

@@ -7,6 +7,10 @@ import com.fasterxml.jackson.databind.`annotation`.JsonDeserialize
 import com.fasterxml.jackson.databind.`annotation`.JsonPOJOBuilder
 import com.netflix.graphql.dgs.codegen.cases.constantsForInputTypes.expected.Generated
 import java.lang.IllegalStateException
+import kotlin.Any
+import kotlin.Boolean
+import kotlin.Int
+import kotlin.String
 import kotlin.collections.List
 import kotlin.jvm.JvmName
 
@@ -22,6 +26,22 @@ public class Query(
   public val people: List<Person?>?
     get() = __people.invoke()
 
+  private fun `__$fieldValues`(): List<Any?> = listOf(
+      if (__people === peopleDefault) peopleDefault else people,
+  )
+
+  override fun equals(other: Any?): Boolean = this === other || (other is Query &&
+      `__$fieldValues`() == other.`__$fieldValues`())
+
+  override fun hashCode(): Int = `__$fieldValues`().hashCode()
+
+  private fun `__$fieldStrings`(): List<String> = listOfNotNull(
+      if (__people === peopleDefault) null else "people=" + people,
+  )
+
+  override fun toString(): String = `__$fieldStrings`().joinToString(prefix = "Query(", postfix =
+      ")")
+
   @Generated
   public companion object {
     private val peopleDefault: () -> List<Person?>? = 

graphql-dgs-codegen-core/src/integTest/kotlin/com/netflix/graphql/dgs/codegen/cases/constantsWithExtendedInputTypes/expected/types/Person.kt

@@ -7,7 +7,11 @@ import com.fasterxml.jackson.databind.`annotation`.JsonDeserialize
 import com.fasterxml.jackson.databind.`annotation`.JsonPOJOBuilder
 import com.netflix.graphql.dgs.codegen.cases.constantsWithExtendedInputTypes.expected.Generated
 import java.lang.IllegalStateException
+import kotlin.Any
+import kotlin.Boolean
+import kotlin.Int
 import kotlin.String
+import kotlin.collections.List
 import kotlin.jvm.JvmName
 
 @Generated
@@ -29,6 +33,24 @@ public class Person(
   public val lastname: String?
     get() = __lastname.invoke()
 
+  private fun `__$fieldValues`(): List<Any?> = listOf(
+      if (__firstname === firstnameDefault) firstnameDefault else firstname,
+      if (__lastname === lastnameDefault) lastnameDefault else lastname,
+  )
+
+  override fun equals(other: Any?): Boolean = this === other || (other is Person &&
+      `__$fieldValues`() == other.`__$fieldValues`())
+
+  override fun hashCode(): Int = `__$fieldValues`().hashCode()
+
+  private fun `__$fieldStrings`(): List<String> = listOfNotNull(
+      if (__firstname === firstnameDefault) null else "firstname=" + firstname,
+      if (__lastname === lastnameDefault) null else "lastname=" + lastname,
+  )
+
+  override fun toString(): String = `__$fieldStrings`().joinToString(prefix = "Person(", postfix =
+      ")")
+
   @Generated
   public companion object {
     private val firstnameDefault: () -> String? = 

graphql-dgs-codegen-core/src/integTest/kotlin/com/netflix/graphql/dgs/codegen/cases/constantsWithExtendedInputTypes/expected/types/Query.kt

@@ -7,6 +7,10 @@ import com.fasterxml.jackson.databind.`annotation`.JsonDeserialize
 import com.fasterxml.jackson.databind.`annotation`.JsonPOJOBuilder
 import com.netflix.graphql.dgs.codegen.cases.constantsWithExtendedInputTypes.expected.Generated
 import java.lang.IllegalStateException
+import kotlin.Any
+import kotlin.Boolean
+import kotlin.Int
+import kotlin.String
 import kotlin.collections.List
 import kotlin.jvm.JvmName
 
@@ -22,6 +26,22 @@ public class Query(
   public val people: List<Person?>?
     get() = __people.invoke()
 
+  private fun `__$fieldValues`(): List<Any?> = listOf(
+      if (__people === peopleDefault) peopleDefault else people,
+  )
+
+  override fun equals(other: Any?): Boolean = this === other || (other is Query &&
+      `__$fieldValues`() == other.`__$fieldValues`())
+
+  override fun hashCode(): Int = `__$fieldValues`().hashCode()
+
+  private fun `__$fieldStrings`(): List<String> = listOfNotNull(
+      if (__people === peopleDefault) null else "people=" + people,
+  )
+
+  override fun toString(): String = `__$fieldStrings`().joinToString(prefix = "Query(", postfix =
+      ")")
+
   @Generated
   public companion object {
     private val peopleDefault: () -> List<Person?>? = 

graphql-dgs-codegen-core/src/integTest/kotlin/com/netflix/graphql/dgs/codegen/cases/constantsWithExtendedInterface/expected/types/Query.kt

@@ -7,6 +7,10 @@ import com.fasterxml.jackson.databind.`annotation`.JsonDeserialize
 import com.fasterxml.jackson.databind.`annotation`.JsonPOJOBuilder
 import com.netflix.graphql.dgs.codegen.cases.constantsWithExtendedInterface.expected.Generated
 import java.lang.IllegalStateException
+import kotlin.Any
+import kotlin.Boolean
+import kotlin.Int
+import kotlin.String
 import kotlin.collections.List
 import kotlin.jvm.JvmName
 
@@ -22,6 +26,22 @@ public class Query(
   public val people: List<Person?>?
     get() = __people.invoke()
 
+  private fun `__$fieldValues`(): List<Any?> = listOf(
+      if (__people === peopleDefault) peopleDefault else people,
+  )
+
+  override fun equals(other: Any?): Boolean = this === other || (other is Query &&
+      `__$fieldValues`() == other.`__$fieldValues`())
+
+  override fun hashCode(): Int = `__$fieldValues`().hashCode()
+
+  private fun `__$fieldStrings`(): List<String> = listOfNotNull(
+      if (__people === peopleDefault) null else "people=" + people,
+  )
+
+  override fun toString(): String = `__$fieldStrings`().joinToString(prefix = "Query(", postfix =
+      ")")
+
   @Generated
   public companion object {
     private val peopleDefault: () -> List<Person?>? = 

graphql-dgs-codegen-core/src/integTest/kotlin/com/netflix/graphql/dgs/codegen/cases/constantsWithExtendedQuery/expected/types/Person.kt

@@ -7,7 +7,11 @@ import com.fasterxml.jackson.databind.`annotation`.JsonDeserialize
 import com.fasterxml.jackson.databind.`annotation`.JsonPOJOBuilder
 import com.netflix.graphql.dgs.codegen.cases.constantsWithExtendedQuery.expected.Generated
 import java.lang.IllegalStateException
+import kotlin.Any
+import kotlin.Boolean
+import kotlin.Int
 import kotlin.String
+import kotlin.collections.List
 import kotlin.jvm.JvmName
 
 @Generated
@@ -29,6 +33,24 @@ public class Person(
   public val lastname: String?
     get() = __lastname.invoke()
 
+  private fun `__$fieldValues`(): List<Any?> = listOf(
+      if (__firstname === firstnameDefault) firstnameDefault else firstname,
+      if (__lastname === lastnameDefault) lastnameDefault else lastname,
+  )
+
+  override fun equals(other: Any?): Boolean = this === other || (other is Person &&
+      `__$fieldValues`() == other.`__$fieldValues`())
+
+  override fun hashCode(): Int = `__$fieldValues`().hashCode()
+
+  private fun `__$fieldStrings`(): List<String> = listOfNotNull(
+      if (__firstname === firstnameDefault) null else "firstname=" + firstname,
+      if (__lastname === lastnameDefault) null else "lastname=" + lastname,
+  )
+
+  override fun toString(): String = `__$fieldStrings`().joinToString(prefix = "Person(", postfix =
+      ")")
+
   @Generated
   public companion object {
     private val firstnameDefault: () -> String? = 

graphql-dgs-codegen-core/src/integTest/kotlin/com/netflix/graphql/dgs/codegen/cases/constantsWithExtendedQuery/expected/types/Query.kt

@@ -7,6 +7,10 @@ import com.fasterxml.jackson.databind.`annotation`.JsonDeserialize
 import com.fasterxml.jackson.databind.`annotation`.JsonPOJOBuilder
 import com.netflix.graphql.dgs.codegen.cases.constantsWithExtendedQuery.expected.Generated
 import java.lang.IllegalStateException
+import kotlin.Any
+import kotlin.Boolean
+import kotlin.Int
+import kotlin.String
 import kotlin.collections.List
 import kotlin.jvm.JvmName
 
@@ -29,6 +33,24 @@ public class Query(
   public val friends: List<Person?>?
     get() = __friends.invoke()
 
+  private fun `__$fieldValues`(): List<Any?> = listOf(
+      if (__people === peopleDefault) peopleDefault else people,
+      if (__friends === friendsDefault) friendsDefault else friends,
+  )
+
+  override fun equals(other: Any?): Boolean = this === other || (other is Query &&
+      `__$fieldValues`() == other.`__$fieldValues`())
+
+  override fun hashCode(): Int = `__$fieldValues`().hashCode()
+
+  private fun `__$fieldStrings`(): List<String> = listOfNotNull(
+      if (__people === peopleDefault) null else "people=" + people,
+      if (__friends === friendsDefault) null else "friends=" + friends,
+  )
+
+  override fun toString(): String = `__$fieldStrings`().joinToString(prefix = "Query(", postfix =
+      ")")
+
   @Generated
   public companion object {
     private val peopleDefault: () -> List<Person?>? = 

graphql-dgs-codegen-core/src/integTest/kotlin/com/netflix/graphql/dgs/codegen/cases/constantsWithExtendedTypes/expected/types/Person.kt

@@ -7,7 +7,11 @@ import com.fasterxml.jackson.databind.`annotation`.JsonDeserialize
 import com.fasterxml.jackson.databind.`annotation`.JsonPOJOBuilder
 import com.netflix.graphql.dgs.codegen.cases.constantsWithExtendedTypes.expected.Generated
 import java.lang.IllegalStateException
+import kotlin.Any
+import kotlin.Boolean
+import kotlin.Int
 import kotlin.String
+import kotlin.collections.List
 import kotlin.jvm.JvmName
 
 @Generated
@@ -36,6 +40,26 @@ public class Person(
   public val email: String?
     get() = __email.invoke()
 
+  private fun `__$fieldValues`(): List<Any?> = listOf(
+      if (__firstname === firstnameDefault) firstnameDefault else firstname,
+      if (__lastname === lastnameDefault) lastnameDefault else lastname,
+      if (__email === emailDefault) emailDefault else email,
+  )
+
+  override fun equals(other: Any?): Boolean = this === other || (other is Person &&
+      `__$fieldValues`() == other.`__$fieldValues`())
+
+  override fun hashCode(): Int = `__$fieldValues`().hashCode()
+
+  private fun `__$fieldStrings`(): List<String> = listOfNotNull(
+      if (__firstname === firstnameDefault) null else "firstname=" + firstname,
+      if (__lastname === lastnameDefault) null else "lastname=" + lastname,
+      if (__email === emailDefault) null else "email=" + email,
+  )
+
+  override fun toString(): String = `__$fieldStrings`().joinToString(prefix = "Person(", postfix =
+      ")")
+
   @Generated
   public companion object {
     private val firstnameDefault: () -> String? = 

graphql-dgs-codegen-core/src/integTest/kotlin/com/netflix/graphql/dgs/codegen/cases/constantsWithExtendedTypes/expected/types/Query.kt

@@ -7,6 +7,10 @@ import com.fasterxml.jackson.databind.`annotation`.JsonDeserialize
 import com.fasterxml.jackson.databind.`annotation`.JsonPOJOBuilder
 import com.netflix.graphql.dgs.codegen.cases.constantsWithExtendedTypes.expected.Generated
 import java.lang.IllegalStateException
+import kotlin.Any
+import kotlin.Boolean
+import kotlin.Int
+import kotlin.String
 import kotlin.collections.List
 import kotlin.jvm.JvmName
 
@@ -22,6 +26,22 @@ public class Query(
   public val people: List<Person?>?
     get() = __people.invoke()
 
+  private fun `__$fieldValues`(): List<Any?> = listOf(
+      if (__people === peopleDefault) peopleDefault else people,
+  )
+
+  override fun equals(other: Any?): Boolean = this === other || (other is Query &&
+      `__$fieldValues`() == other.`__$fieldValues`())
+
+  override fun hashCode(): Int = `__$fieldValues`().hashCode()
+
+  private fun `__$fieldStrings`(): List<String> = listOfNotNull(
+      if (__people === peopleDefault) null else "people=" + people,
+  )
+
+  override fun toString(): String = `__$fieldStrings`().joinToString(prefix = "Query(", postfix =
+      ")")
+
   @Generated
   public companion object {
     private val peopleDefault: () -> List<Person?>? =